[Sema] Fix -Wuninitialized for struct assignment from GNU C statement expression

Summary:
Do not automatically report self references of structs in statement expression
as warnings. Instead wait for uninitialized cfg analysis.
https://bugs.llvm.org/show_bug.cgi?id=42604

Reviewers: aaron.ballman, rsmith, nickdesaulniers

Reviewed By: aaron.ballman, nickdesaulniers

Subscribers: nathanchance, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64678

llvm-svn: 367134

1 files changed, 6 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 1c7b2b0ae27..2e82dcf4ac8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11257,9 +11257,12 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
   // Check for self-references within variable initializers.
   // Variables declared within a function/method body (except for references)
   // are handled by a dataflow analysis.
-  if (!VDecl->hasLocalStorage() || VDecl->getType()->isRecordType() ||
-      VDecl->getType()->isReferenceType()) {
-    CheckSelfReference(*this, RealDecl, Init, DirectInit);
+  // This is undefined behavior in C++, but valid in C.
+  if (getLangOpts().CPlusPlus) {
+    if (!VDecl->hasLocalStorage() || VDecl->getType()->isRecordType() ||
+        VDecl->getType()->isReferenceType()) {
+      CheckSelfReference(*this, RealDecl, Init, DirectInit);
+    }
   }
 
   // If the type changed, it means we had an incomplete type that was